Proposed as a system which detects a position of a terminal or the like attached to a moving body such as a person or an object is a system which uses GPS, radio LAN, RFID, infrared, ultrasonic or the like. Recited in Non-Patent Literature 1, for example, is the system which detects a position of a terminal attached to a moving body by using various kinds of media such as radio, ultrasonic and infrared.
Proposed is a technique for using, in a system using a radio machine such as radio LAN or RFID among such position detection systems, a radio machine for reference which is disposed in an environment and has the same function as that of a device attached to a moving body in order to increase precision and decrease costs for its position detection.
As a technique of this kind, recited in Non-Patent Literature 2, for example, is related art which realizes highly precise tag position coordinate estimation in an active RFID system by referring to tags disposed densely in an environment.
On the other hand, recited in Patent Literature 1 is related art which realizes a position detection system at low costs by comparing a radio condition measured by a radio machine attached to a moving body and a radio condition measured by a radio machine for reference which is disposed in each area in advance.    Non-Patent Literature 1: G. Chen and D. Kotz, “A Survey of Context-Aware Mobile Computing Research”, Technical Report 381, Department of Computer Science, Dartmouth College 2000.    Non-Patent Literature 2: Lionel M. Ni, Yunhao Liu, Yiu Cho Lau and Abhishek P. Patil, LANDMARC: Indoor Location Sensing Using Active RFID, PerCom 2003.    Non-Patent Literature 3: Kohonen, Self-Organizing Map, Schuplinger•Farelark Tokyo Co. Ltd., June 2005.    Patent Literature 1: Japanese Patent Laying-Open No. 2006-308361.
Problem of the position detection systems recited in the above-described Non-Patent Literature 1 and 2 and Patent Literature 1 and the like is incapability for correct detection of a position of a radio machine attached to a moving body when the number of radio machines for reference which are disposed in an environment is small.
The reason is that a difference between a radio condition measured by a radio machine for reference and a radio condition measured by a radio machine attached to a moving body becomes larger due to characteristics of radio environments derived from a dynamic hindrance in the environment or a manner of attachment of the radio machine to the moving body.